With the development of electronic information technology, the miniaturization and densification of electronic equipment installation, the high capacity and high frequency of information, in recent years, higher demands are put forward for the overall performances of circuit substrates, such as thermal resistance, water absorption, chemical resistance, mechanical property, size stability, and dielectric properties.
As to the dielectric properties, the transmission rate of signals and the dielectric constant Dk of insulating materials in high frequency circuits have the following relation, i.e., the lower the dielectric constant Dk of insulating materials is, the faster the transmission rate of signals is. Thus, substrates having low dielectric constant need to be developed to achieve high speed of the transmission rate of signals. Along with high frequency of the signal frequency, the signal loss in the substrates cannot be ignored. The signal loss and frequency, dielectric constant Dk, dielectric loss factor Df have the following relation, i.e., the lower the dielectric constant Dk of the substrates and the dielectric loss factor Df are, the lower the signal loss is. Therefore it has become a common research direction for CCL manufacturers to develop high frequency circuit substrates having low dielectric constant Dk and low dielectric loss factor Df and having better thermal resistance.
In the molecular structure of polyphenylether resin, there are a large amount of benzene ring structures and there is no strong polar group, which gives polyphenylether resin with excellent properties, e.g., high glass transition temperature, better size stability, low linear expansion coefficient, low water absorption, especially excellent low dielectric constant, and low dielectric loss. However, polyphenylether as a thermoplastic resin has the shortcomings of high resin melting point, worse processing performance, worse solvent resistance and the like. Excellent physical properties, thermal resistance, chemical properties and electrical properties of polyphenylether attract the world's major companies to make modifications and certain achievements have been made. For example, active groups are introduced to the chain ends or side chains of polyphenylether molecules to make them become a thermosetting resin. After thermosetting, the resin has excellent overall properties, such as thermal resistance and dielectric properties, and it becomes an ideal material for preparing high frequency circuit substrates.
The curable modified polyphenylether resin having active groups at the end of the molecular chain or at the side chain is generally applied in high frequency circuit substrates in combination with crosslinking agent to compose a resin composition. The crosslinking agent has active groups capable of reacting with the modified polyphenylether. According to the document research, the common crosslinking agents are polybutadiene, butadiene styrol copolymer and the like for modified polyphenylether having C═C double bonds. For example, CN101370866A, CN102161823, and CN102304264 disclose using polybutadiene or butadiene styrol copolymer as the crosslinking agent for modified polyphenylether to prepare high frequency circuit substrates. Although the boards have excellent overall properties, such as dielectric properties, polybutadiene or butadiene styrol copolymer decreases the thermal resistance and interstratified adhesive force of the boards.
Using organosilicon compounds containing unsaturated double bonds as the crosslinking agent for modified polyphenylether can solve the problems of insufficient thermal resistance and interstratified adhesive force of the boards brought by polybutadiene or butadiene styrol copolymer as the polyphenylether crosslinking agent. CN102993683 discloses preparing the crosslinking agent for modified polyphenylether by using organosilicon compounds containing unsaturated double bonds. The high frequency circuit substrates prepared therefrom have a high glass transition temperature, a high thermal decomposition temperature, a high interstratified adhesive force, a low dielectric constant and a low dielectric loss tangent, and are very suitable as the circuit substrates for high frequency electronic equipments.
CN102993683 discloses that organosilicon compounds containing unsaturated double bonds used therein are linear or annular organosilicon compounds. Linear organosilicon compounds containing unsaturated double bonds have a better flexibility, and the high frequency circuit substrates prepared therefrom have a lower bending strength. The circuit substrates prepared from annular organosilicon compounds containing unsaturated double bonds have better overall properties, but the organosilicon compounds easily evaporate due to low molecular weight.